This invention relates in general to an electric power controller for providing electrical power to an electrical load, and more particularly to a universal controller that accepts any one of a variety of different input voltage waveforms, magnitudes, and frequencies, and, under computer program control, provides a controllable output voltage to any one of a variety of different electrical loads that include, among others, AC and DC motors.
Electrically powered devices have a wide variety of voltage, current and control requirements. Some types of electrically powered devices require an AC operating voltage having a fixed frequency and a fixed magnitude. Others require an AC operating voltage having a fixed magnitude and a variable frequency or an AC voltage having a variable magnitude and a fixed frequency. Similarly, some types of electrically powered devices require a DC voltage having a fixed or variable magnitude and/or a polarity that can be reversed. In many cases, these devices can be operated by a DC voltage which can be chopped or pulse width modulated. Still other types of electrically powered devices, such as AC/DC motors, can operate from AC or DC sources.
Electrical power sources also have a wide variety of types. Some types of power sources provide single or multiple phase AC voltages and currents at fixed frequencies and magnitudes. Fixed frequency AC sources typically provide a selectable one of a plurality of frequencies, 50 Hz single and multiple phase AC voltages being widely used in Europe, while 60 Hz single and multiple phase AC voltages are widely used in North America. Depending only on the application, AC sources typically provide a selectable one of a plurality of magnitudes, such as 220 or 440 volts, among others. Similarly DC power sources come in a variety of different types having different magnitudes and reversible or non-reversible polarities. Some DC sources, such as batteries, provide a virtually ripple free DC voltage having a fixed magnitude. Others, such as DC to DC converters are able to operate from variable magnitude DC input voltages or to provide variable magnitude DC output voltages.
Prior to the present invention, it was common to deal with these differing load requirements and source types by stocking a variety of different types of power conversion and control devices, including transformers, controlled rectifier devices, inverters, voltage regulators, DC to DC converters and various combinations thereof. With this approach, it was necessary to stock devices having various combinations of input and output voltage ranges. In applications involving the control of motors, this approach is made even more difficult by the fact that motors come in a variety of types having different input voltage and load current requirements and different control requirements. As a result, the task of designing and stocking power conversion and control devices that are dedicated to operating with each of a variety of different types of motors and each of a variety of different types of power sources is a daunting and expensive one.
It will therefore be seen that there exists a need for a power conversion and control device that is able to operate from any one of a variety of different types and magnitudes of power sources and to meet the power and control requirements of any one of a variety of different types of loads.